Lice infestation of the human body is an enduring problem of the ages, with reference being made to these pests throughout recorded history. As noted by Cardin, et al., in U.S. Pat. No. 5,292,504, the spread of typhus has been attributed to lice, decimating both armies and navies of the 15th through 18th centuries. Even today lice present a source of serious health problems worldwide. Not only do lice carry a variety of bacteria on their outer surfaces, but in their fecal matter as well. Lice transmit bacteria to the human host through puncture wounds inflicted during feeding. U.S. Pat. No. 5,547,665 issued to Upton reveals that lice infestation can cause such ailments as staphylococcal skin infections, typhus, trench fever and relapsing fever.
The human lice genus includes head-, body-, and pubic lice, each of which has specific characteristics in their habitat and feeding. Lice are capable of spreading rapidly. A fertilized female lays about six to eight eggs every 24 hours. It has been estimated that a single female louse and her daughters could have 112,778 offspring in a period of 48 days. The present invention is of primary use in the elimination of the eggs (nits) of head lice.
The head louse (pediculus humanus capitis) clings to the hair shaft when feeding, mating and laying eggs. Removal of nits is particularly difficult, as each nit is cemented to a shaft of hair by a glycoprotein glue, acting as a binding cement. Lice eggs themselves are covered by a chitinous sheath which surrounds both the nit and the attached hair shaft. Thus, removal of nits requires separation from individual shafts of hair.
Various methods and compositions for the removal of head lice from hair are known. Certainly, the manual removal of lice through the use of a fine-toothed comb or tweezers has been employed for years. In addition, a number of insecticides (known in this application as pediculicides) have been developed for killing lice, thereby substantially alleviating reproduction. Pediculicides, such as lindane and various pyrethrins, have been used in conjunction with shampoos for killing and rinsing out lice. However, as noted by Upton in U.S. Pat. No. 5,547,665, the use of these methods and compositions is not entirely effective in controlling head lice, as some lice often survive the treatment. Indeed, the National Pediculosis Association has reported that 20 to 80 percent of nits survive initial pediculicide treatment, resulting in reinfestation.
Pyrethrum, permethrin and lindane pesticides, the only FDA approved pesticides for lice, all work as central nervous system (CNS) toxins on lice. Their effectiveness depends on their ability to reach the functioning CNS of lice. Unfortunately, lice eggs do not develop a functioning CNS until they are between three and four days old, during an average incubation period of approximately ten days. As a result, only 60% to 70% of eggs treated can be killed upon application of one of these pesticides. The only absolutely certain method for eliminating a lice infestation is the removal of all remaining eggs after treatment.
Adding to the difficulty of removing nits is their virtually microscopic size, and the fact that the color of their keratinous shell tends to blend into the subject's hair and scalp background. Thus, nits can be extremely difficult not only to remove, but even to locate.
In recent years several compositions have been developed which are claimed to swell the nit around the hair shaft in order to facilitate removal by combing. One such patent is U.S. Pat. No. 4,927,813 issued to Bernstein. This patent employs the noxious agent formic acid in a pharmaceutically--acceptable carrier applied to a patient's hair and scalp for a period of time sufficient to effect swelling. This application is followed by washing and rinsing in order to remove the detached nits. The distributors of one such commercial product, containing 8% formic acid, has reported that five minutes of combing after treatment has led to a 93.5% removal of nits. While impressive, the remaining 6.5% nits remain viable and could potentially reproduce rapidly and reinfest the subject.
A more recent patent, U.S. Pat. No. 5,547,665 issued to Upton discloses a water-based enzyme composition which causes swelling and/or biodegrading of the complex organic cement that binds nits to hair in order to facilitate their removal. Whether or not this enzyme composition is completely effective in causing swelling of all nits, it is still contemplated that the loosened nits would be physically removed from the host following application of the enzyme, by a process of combing or nit-picking. Thus, these inventions do not completely remove the difficulty in locating and extracting nits from the subject's hair.
U.S. Pat. No. 5,658,750, issued to Sheftel, discloses methods for detecting louse infestations and monitoring the course and effectiveness of pediculicide treatments. This involves removal of hair samples containing nits or suspected nits themselves and subjecting the removed materials to a vital indicator to provide a visual, colorimetric indication of their viability. In one embodiment, the degree of color change of the isolated material indicates the degree of cell viability, and in another embodiment, a color is preferentially taken up by either live or dead cells in contrast to the other. This method, however, will only characterize the viability of those nits that are removed with excised hair samples, from which only conjecture can be made about the viability of the remaining nits. Further, without removal of copious hair samples from many different parts of the head, the method leaves considerable doubt about the potential for reinfestation.
It should also be noted that the prior art, even in disclosing methods of killing head lice, does not solve the historical problem of manually removing even dead lice or nits. It is self evident that the continuing presence of large numbers of even dead nits can be emotionally distressing to both the patient and his or her family. Further, the process of manually removing nits is tedious, time consuming, and potentially even painful.
Other methods have been produced to aid in the removal of head lice. Typical of the art are those devices disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. Inventor(s) Issue Date ______________________________________ 4,439,427 Bernstein March 27, 1984 5,292,504 Cardin, et al. March 8, 1994 5,380,756 Andrews, et al. January 10, 1995 5,681,859 James, et al. October 28, 1997 ______________________________________
Again, these devices in no way facilitate the visible detection of nits so as to ease the process of physical removal.
The present invention results from efforts to devise some means to ensure the complete removal of nits from hair, whether pretreated by pediculicide or not, in order to reduce to a small probability that such nits will remain undetected on the scalp or hair and subsequently reinfest the patient. While pretreatment of the scalp with an agent that loosens nits from the hair shaft may facilitate their removal by subsequent combing, where the comb must contact each such nit-bearing hair shaft, it is obvious that without such contact the nit will most likely remain on the hair. This fact lead to our search for agents which can preferentially target the nits and in some manner enable them to be visually discerned against the subject's hair and scalp background. With this accomplished, the comber could individually detect and efficiently remove each of the nits.
The desired agents must have a specific affinity for the chitinous, poly (N-Acetyl-D-Glucosamine) shell of the nit and/or the binding cement, and less so for the keratinous, protein hair shaft, in order to provide the differentiation. Additionally, the desired agents should be readily visible at the low concentrations in which they would be present on the tiny nit surface, following some suitable method of application. A further requirement would be their dermal and respiratory safety, at the concentrations at which they would be applied to the subject in some suitable solubilizing and/or suspending medium. The resulting invention, described below, satisfies these needs and provides additional advantages which shall become apparent.
Objects of the Invention
It is, therefore, an object of the present invention to provide compositions which can be applied to the subject to enable nits on hair to be better visualized in order to facilitate the removal process.
It is a further object of the present invention to identify those visualants which have high perceptibility at low concentrations, and which are characterized by an affinity to nit surfaces and/or the binding cement, so that they may be seen against the background of the patient's scalp and a diversity of hair colorations.
It is an additional object of the present invention to identify compositions which are safe to humans and have sufficient solubilities and safe solvents to enable them to be applied to humans without harm.
In addition, it is an object of the present invention to provide safe compositions which serve as visualants for nits, but which can easily be rinsed from the hair and scalp of the subject so as to avoid the embarrassment of an unwanted coloration.
It is a further object of the present invention to provide a method for the removal of nits which involves the easy and safe application of compositions which serve as visualants for nits so as to facilitate their removal.
It is finally an object of the present invention to augment the success of nit-softening agents designed for nit removal by enabling nits to be seen by an individual attempting to complete their physical removal and, therefore, greatly minimize the probability of reinfestation.